Consolidated Statements of Comprehensive (Loss) Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Comprehensive income attributable to common stockholders
Net (loss) income	$ (747)	$ 10,579	$ 4,235
Other comprehensive (loss) income:
Unrealized (loss) gain on available-for-sale securities	(46)	440	(191)
Benefit plan adjustments	(215)	135	(189)
Unrealized interest rate swap (loss) gain	(3,213)	(2,809)	988
Other comprehensive (loss) income before taxes	(4,096)	(2,658)	565
Benefit (provision) for income taxes related to other comprehensive income items	1,147	744	(158)
Other comprehensive (loss) income	(2,949)	(1,914)	407
Comprehensive (loss) income	(3,696)	8,665	4,642
Comprehensive loss attributable to non-controlling interests	(7)	(1)	(20)
Comprehensive (loss) income attributable to common stockholders	(3,689)	8,666	4,662
SERP liability adjustments
Other comprehensive (loss) income:
Benefit plan adjustments	$ (622)	$ (424)	$ (43)